SD and MicroSD cards use a type of memory (Flash RAM) that is subject to wearing out -- the actual memory cells deteriorate very slightly each time data is written to them, and SD, MicroSD, and thumb drives typically don't use the very best flash RAM (as would hopefully be the case for internal Solid State Drives that house the operating system and user storage in your computer).
Further, the constant plugging and unplugging of these cards also puts wear on the connectors.
Either of these factors can result in one or more devices losing the ability to read the card, and this can result in only old files being accessible (though it's much more common for the card to become read-only, or even become unreadable).
If you can still read the original card in your computer, please make a complete copy of the contents immediately, and then write those contents to a new card (as well as keeping a copy on your computer's storage) -- and throw the old card away, so you don't accidentally use it for anything.